Heat transfer across a scraped surface

Abstract

Investigations using three experimental scraped surface falling film vertical heat exchanger tubes (6 in., 12 in. and 24 in. by 1 in. D.) have been made. Water and water‐glycerol mixtures have been heated in the tubes by passing them down the heated inside surface which was continuously scraped by rotating blades. Flowrates between 306 lb/hr.ft. and 1070 lb/hr.ft. were used, the rate of rotation was varied from 370 to 1600 rpm whilst the number of blades on the shaft was varied between 1 and 4. As a result of these experiments the following equation accurate within ± 20% is proposed for correlating the heat transfer coefficient in the range of the variables studied: Visual observations of the flow of the liquid down the tube indicate that the liquid is held as a continuous fillet in front of each blade. This fact is used in the Appendix* for the alternative suggestion for the characteristic dimension in the correlation.

Heat Transfer of Dilute Polyacrylamide Solutions in Flattened Tube Exchangers

“…This can be achieved by physical scraping of the exchanger wall surface, as demonstrated by Bott [1], Bott and Romero [2], Chong [3], D'Addio et al [4], Tähti [5], and Yataghene et al [6]. Pattenden and Richards [7] showed that another way of achieving the same effect was by rotating the exchanger tubes.…”

Determination of optimum aspect ratio for laminar flow heat transfer of dilute viscoelastic solutions in flattened tube heat exchangers

“…Bott [1,2], Bott and Romero [3], Chong [4] and Tähti [5] demonstrated this by scraping the exchanger surface. The heat exchanger could also be vibrated as demonstrated by Song [6], or electrostatic forces could also be applied as shown by Nassauer and Kessler [7].…”

HYDRODYNAMICS and HEAT TRANSFER IN THIN FILM SCRAPED SURFACE HEAT EXCHANGERS — A REVIEW

“…Again, the limitation of this theory is that it assumes the need for good mixing for heat transfer to viscous liquids and hence predicts higher coefficients than those obtained in practice. Bott and Romero (1963) studied heat transfer to nonboiling water and water-glycerol mixtures inside a scraped surface, falling film vertical heat exchanger. The flow rates were 0.039-0.133 kg/s.…”